Method and apparatus for rapidly drying casein curd and like substances



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METHOD AND APIAR ATUS FOR RAPIDLY DRYING CASEIN CURD AND LIKE SUBSTANCES Filed April 8, 1941 2 Sheets-Sheet 1 ad 1 I" .1. I 1ai1 10' 20 ii April 13, 1943 W. B. WINTER METHOD AND APPARATUS FOR RAPIDLY DRYING CASEIN GURD AND LIKE SUBSTANCES Filed April 8, 1941 2 Shets-Sheet 2 lNVENIOR Killian; .Blfinlqr PatentedApr. 13, 1943 UNITED STATES PATENT oFri-ca 7 METHOD AND Aif:2:12. JS FOR RAPIDLY mums casnm sranons CUR!) AND LIKE- SUB- William 1;. Winter, Belmont, Mass assignor to Atlantic Research Associates, Inc.,

Newtonviile,

Mass, a corporation of Delaware Application April 8, 1941, Serial No. 387,453 15 Claims. (01. 34-10),

This invention relates to an improved method and apparatus for rapidly drying solid particles of moist substances suspended in a stream of heated air.

It has heretofore been proposed to dry moist materials such as casein ando'ther substances by feeding the materials in a finely divided state for suspension in a stream of heated air. The

equipment proposed included a large and'costly layout of tubing of considerable length and size which required a large installation space. While this heretofore proposed method of drying has materially reduced the time required as compared with the tray and tunnel and rotary" types of driers, it is nevertheless objectionable, for the capacity it provides, as constituting bulky and relatively costly apparatus.

One of the objects of the present invention, therefore, is to provide an improved method of and apparatus for rapidly drying in a stream of heated air moist particles of substances wherein.

the apparatus for a given capacity requires less installation space than drying apparatus of similar character heretofore proposed.

Another object of the invention is to provide an improved method of and apparatus for rapidly drying in a stream of. heated air particles of moist substances at a power consumption for a given capacity considerably less than required by drying apparatus of similar character heretofore proposed.

Another object of the invention is to provide an improved method and apparatus for drying moist substances wherein a great versatility of control is provided.

A further object of the invention is to provide an improved method and apparatus for drying small particles of wet substances wherein the particles are given individual treatment in accordance to the amount of drying required.

A still further object of the invention is to provide an improved drying apparatus which is simple, sturdy, compact and relatively economical to build and operate.

Further-objects and advantages of the inven' tion will become apparent from the following description of the method as well as from a later detailed description of apparatus by which the method can be carried out. i i In its broader aspects, my improved method for rapidly drying solid particles of moist substances comprises feeding small particles of the substance for suspension in'a stream of air heated to a suitable temperature and causing the air and particles entrained therein to move through a chamber in a double vortex movement, whereby the coarser moisture retaining particles after being initially heated are separated from the air in the initial or outer vortex movement. The

finer particles which are substantially dried in cles which are separated from the drying air by the action of gravity and centrifugal force in the outer vortex are intercepted either by an inwardly deflecting surface or by additional drying air to direct and re-entrain the particles for movement in the inner vortex where they can also be carried off in a substantially dried condition for final separation from the air.

The temperature of the heated air initially contacted by the moist particles may be selected from a wide range depending, of course, upon the wetness of the particles to be dried and the effect which high temperatures have upon the quality of the material. For most moist materials a satisfactory temperature can be selected for use in my method above 200 F. and up to as high as 350 is so rapid that the moisture absorbed by the heated air quickly reduces the initial temperature thereof so that when the particleshave given up a large portion of their moisture, the temperature of the surrounding air will have been correspondingly reduced so as not to be injurious to the dried or partially dried material.-

For substances such as casein curd where the qualities thereof can easily be adversely affected by high temperatures and prolonged heating, temperatures as high as 320 F have been used successfully inmy method without adversely affecting the qualities of casein and without any substantial discoloration of the particles.

The additional air introduced into the flowing stream between the outer and inner vortices can be of the same but is usually preferred to be lower than the initial temperature of the main stream of air. The temperature of the additional air, however, will depend upon the final degree of drying desired and the amount of drying accomplished by the main air stream.

Where substance of exceptionally high moisture content is to be dried two or more drying stages can be arranged, the exhaust from the second or third stage may be used in'the first where this material is introduced, or the exhaust F. The drying by my method' the third; or the stages may be connected in any other arrangement depending upon the temperacan be subjected by my method to air of a temperature of 320 F. in the first stage without adversely affecting the quality thereof. The casein discharged from the flrst stage would then have a temperature of about 100 F. and be about one-half dry, that is, reduced to a moisture content of about 30 to 35%. With this moisture content, the particles can be successfully subjected in the second stage to air temperatures also as high as 320 F. and should the moisture content "of the particles the heated air for the second stage can be tempered by admixing therewith exhaust air from the first-stage. I

Whether or not the same temperature is used for the air fed to each of a plurality of units, or whether or not more than one unit is used will depend upon the size of the particles, the moisture content thereof and the rate of diffu sion of the moisture from the inside to the out-, side of the particles, and also on the load the drier can carry.

Briefly, a-single unit of the apparatus comprises a cyclone chamber similar to that of a cyclone dust and air separator. stream of air and the particles entrained therein flow in a large downward whirl or vortex into the chamber. In the lower portion of the chamber the downward direction of the air movement is reversed, the air and the fines suspended therein being caused to whirl upwardly as a small vortex within the larger vortex. The coarser moisture laden particles which are less easily dried are separated by centrifugal force from the air during movement through ;the outer vortex, the separated particles being further dried and reentrained in the flow by additional air introduced adjacent the bottom of the chamber.

The introduction of additional or secondary air to further dry and reentrain the coarser moisture retaining particles for movement into the inner vortex may be brought about in any one of several ways. The additional air may be taken direct from the same source as the initial air or from the exhaust of the cyclone chamber itself, or from another drying unit and forced or drawh in tangentially at the bottom of the cyclone chamber. Where the additional air is forced into the chamber at the bottom tangential inlet may be provided, or a small cyclone chamber arranged to exhaust directlybe less than 30 to 35%,

thereof, a vertical or The initial 7 particles tending to separate from the air stream the moist particles are subjected to an initial drying step before they are introduced into the double vortex movement. The initial stream of air and entrained particles are first caused to whirl upwardly through a narrow space so that the coarser moisture laden particles, due to their tendency to gravitate downwardly counter to the upward flow of air are tumbled and re-entrained by the incoming heated air. After the stream of air has moved in an upward whirl for a determined distance, the air and entrained particles are caused to whirl through a double vortex movement in a cyclone chamber similarly ,as hereinbefore described.

In the above described method and its several modifications, the drying can be accomplished in a single stage because, although additional quantities of heated air can be introduced, the substance to be dried is not separated completely from the air with which it is initially contacted until the drying is substantially complete. With certain substances and degrees of wetness, two or more stages may be preferred as hereinbefore stated.

' The drying with the doublevortex movement for each stage of drying not only greatly reduces the size and number of chambers and therefore the installation space heretofore required for particle suspension driers, but a considerable saving in power consumption for a given capacity is also effected by my invention. This saving in power consumption is effected by utilizing the inner vortex of the cyclone chambers to prolong the contact relation between the heated air and the particles. The additional air introduced into the inner vortex serves to convey the substance to be dried into the inner vortex and can be used to add or lower the heat, and humidify or lower the humidity.

A better understanding of the method and of the forms of apparatus that can be used to carry out the method will become further apparent upon consideration of the following detailed description when taken in connection with the accarrying out the method of my invention; Figure into the lower end of the main cyclone chamber and thereby pick up the gravitating particles and carry them into the inner vortex. Then again, the additional air might be forced into the inner .vortex by providing an axial flow fan'or air current straightening vanes at the bottom .of the cyclone chamber.

If suction is relied upon the air streams, this may be carried out by providing a suitable fan at the exhaust duct, the

introduction of the initial and additional airstreams being controlled by suitably located dampers.

for introduction of 2 is a plan view of the apparatus showing a separator construction;

Figure 3 is-a fragmentary view in vertical section showing a modified form of the invention;

Figure 4 is a fragmentary view in elevation, partially in section, showing another embodiment of the apparatus; and

Figure 5 is a view in elevation, partially in section, and showing a further form of apparatus by whichthe method of my invention may be practiced.

Referring to Figures 1 and 2 of the drawings, a compact drier construction is shown comprising a casing 8 defining a conically shaped cyclone chamber l0 similar to a centrifugal dust and air separator. The chamber It) has a tangential inlet l2 and a centrally disposed exhaust duct 14 extending through the upper portion thereof to a separator 30.

A stream of heated air is propelled by a power driven fan I6 from a heater l8 through a conduit 20 into which solid particles of wet substance of about 20 to 40 mesh are fed through a duct 22.

. l I 2,316,207 .To facilitate the drying of the coarser particles, 7

.be rolled or otherwise shaped which are not so quickly dried are separated therefrom after initial contact with the air by centrifugal force, provided, of course, that the coarser particles do not have a proportionately higher surface area than thefin er particles. As the air whirls within the drying chamber, it moves downwardly in a large outer vortex 2|, and then upwardly in a smaller vortex 23 centrally of the vortex 2|; The upwardly whirling air together with the suspended particles are carried out of the drying chamber through the duct l4. The coarser moisture retaining partir whirling movement gravitate adjacent 313F315 of the chamber toward the bottom e'of. l

r: order to obtain adequate drying of the coarser particles of substance quickly and before undesirable case hardening thereof is effected, the separated particles are intercepted by an additional stream of heated air introduced adjacent the bottom of the chamber. This can be accomplished in several ways. I One way of accomplishing this, as shown in Fig. 1, ncludes a con duit 24 which is connectedtangentially to the bottom 25 of the main cyclone casing. Heated, air is fed by a fan 26 from the heater 18 through the conduit 24 tangentially into the bottom portion of the chamber It. If desired, the air may be tempered by introduction of cool air at 21.

l The air thus introduced into the bottom of .the

chamber I is given a whirling movement adapted to pick up any particles gravitating to the cles which are separated from the air during the In order to preserve heat, the casing and conduits of the system are-covered by a suitable layer of insulation 56. I

While the incoming air at I2 is introduced tangentially of the chamber to provide a whirling movement for the air and entrained particles,

one or more vanes 60 may be provided to entrain the particles for a longer drying period.

, From the foregoing it will be observed that the particles of substance fed through the duct 22 are rapidly subjected to a high temperature,

whereupon a large percentage of the moisture.

containedin the material is quickly absorbed by the heated air, thereby materially lowering the temperature of the air and partially saturating the same. Since air when substantially saturated has little further rapid drying power, my method and apparatus provides forthe separation from this initial air of at, least those particles which still retain a substantial portion of moisture. The partially saturated air together with the finer particles which are more easily dried are permitted to pass out of the chamber l0 shortly after entrance thereto. retaining particles which have been substantially raised in temperature by the initial drying treatment are intercepted and further treated by an additional stream of heated air of a dryness capable of quickly completing the drying thereof. The drying of the particles, both fine and relatively, coarse, is onlya matter of seconds.

This rapidity of the drying operations, while highly efficient and capable of use in small sized installations, can be advantageously used in the drying of casein curd and similar wet substances, By drying the curd immediately after the washing and pressing operations the increase in bottom thereof and carry them in a whirling.

movement into the inner vortex. I I

Another method by which additional air can be advantageously introduced at the bottom of the chamber I0 is by connecting thereto a smaller cyclone chamber 28, as illustrated in F18: 3. Additional air introduced tangentially mto the chamber 28 whirls upwardly through the bottom 25 of the chamber It) to pick up particles gravitating toward the bottom of the chamber Ill. Should the chamber. l0 become overloaded or receive a quantity of particles too heavy for the air stream to easily reentrain, the bottom cyclone 28 can then receive the overflow. I

In order to insure that th additional air introduced by way of the chamber 28 does not exert too great a centrifugal force upon reentrained particles as the air passes into the chamber ill, the port 36 may be provided with a plurality of air current straightening vanes 38. These vanes translate part of the whirling action of the air into a vertical component which insures the conveyance of the reentramed particles well upwardly into the inner vortex 23. I

The bottom of the chamber 28 is prov1ded with a withdrawal duct 29 whereby foreign and overweight particles may be collected and withdrawn,

at this point, and if desired subjected to a further drying stage. I I

I The exhausting air and entrained particles are conveyed from the duct l4 through the separator 30 whereby the particles are separated from the air, the air being exhausted through the duct 32 -'and the particles through the duct 34. A damper 33 may be used to facilitate the separation.

acidity heretofore experienced in the drying of casein is substantially avoided. The heating period of the drying short, and since the dry product may be immediately subjected to a cooling treatment, un-' usually low viscosity casein can be produced. Conversely, by using auxiliary air to heat treat the casein after drying higher viscosity casein can be produced.

The flow of the air and the particles of material through the drier may be induced by suction as well as by "propulsion. for example, an embodiment of the invention is shown wherein the exhaust duct 40 of the chamber 42 is provided with a fan 44 driven by a motor 45; are drawn into the chamberthrough conduits 46 and 41 by the suction created by the fan 44. Suitably located dampers 48 and 49 control the flow of air through the conduits and 41, the

substance to be dried being fed into the conduit 46 at 50. The exhaust separator 52 which is of the centrifugal type and similar to the separator 30 shown in Figs. 1 and 2 separates the particles from the a-irfor deposit in the bin 54. e I

As shown in Fig. 4, it is sometimes helpful to place a cone-shaped member 60 at the bottom of the drying chamber with the apex thereof ex-' tending upwardly toward the exhaust duct. The cone may be spaced from the walls by suitable spacing rods 62. The cone is preferably located 4 so that the conical surfaces thereof are disposed where the main air stream reverses itselfin passing from the outer to the inner vortices. Thus, should little or no additional air be introduced at the bottom of the chamber, the conical The coarser moisture operation being extremely In Figure 4,

In this embodiment streams of air in arrangement surfaces will intercept and direct the gravitating particles upwardly into the inner vortex.

It is to be understood that the cone 60 may be used, not only in the form shown in Fig. 4, but

also in the forms shown in Figs. 1, 3 and 5.

Referring to Figure 5 of the drawings, a further embodiment of the invention is illustrated dried. A fan 14 propels heated air from a heater 16 through a conduit 18 to which the wet materialin a divided form is fed at 88. The pro-- pelled air entrains the particles of substance and passes into the chamber through a tangential inlet 82.

The initial stream of heated air and entrained particles are caused to whirl upwardly through the annular chamber 10 which is so proportioned as to maintain a steady upward movement of air to an opening 84 which permits passage of the air and entrained particles tangentially into the upper portion of the inner chamber 12. While the finer particles are quickly conveyed through the opening 84 to the chamber 12, the coarser moisture retaining particles tend to resist the upward movement of the air through the chamber I8. These coarser particles tend to gravitate backward against the incoming air, whereby they are further treated before they pass through the opening 84.

, While the drying operation conducted in the chamber 10 may be suflicient to adequately dry part of the solids, further drying and/or heating or cooling treatment may be had in the inner chamber 12. The air and entrained particles entering the chamber 12 pass through whirling movements in substantially the same manner as described in connection with chamber ll) of Fig. 1. Any particles which are of .sufiicient size and weight to separate from the air and gravitate toward the bottom of the chamber 12 are further treated by an upwardly whirling stream of air introduced by a fan 85 through a conduit .86 dis posed tangentially to and near the bottom of the chamber 12. The air introduced through the conduit 86 may be tempered by controlling the admixture therewith of cool air at 81.

A withdrawal duct 88 extending down through the chamber I0 is provided at thebottom of the' chamber 12 through which foreign and overweight particles capable of gravitating through the whirling streams of air maybe collected and withdrawn from the chamber.

A separator 90 is provided similarly as shown in connection with the embodiment illustrated in Figure l for receiving the exhausted air and dry particles from the chamber 12.

While many wet substances can be adequately treated in one drying unit, additional drying units or chambers may be provided as herein-bein the acidity already present in the wet curd.

The dried casein particles are small, porous, fluffy and of a light color. The heating period of the drying process being only a matter of seconds, or

prolonged and intensified if desired, a finished casein product can be obtained with either low or high viscosity characteristics, whichever is required.

While several embodiments and variations of my method and apparatus have been shown and described, it is recognized that many additional embodiments and; variations are possible. It is to be understood, therefore, that the embodimerits shown and descrtbed are to be regarded as illustrations of the invention only and not in restriction thereof.

I claim: I

l. A method of rapidly drying particles of moist solid substances comprising delivering and whirling a stream of heated air to establish a voretx movement, feeding the particles to be dried into the stream of heated air for entrainment into the vortex to dry the particles, separating from the vortex movement by action thereof the slowcr drying particles, removing with air from the vortex movement the substantially dried particles, and introducing additional air into the vortex to intercept and reentrain the separated particles in the vortex movement.

2. A method of rapidly drying particles of moist solid substances com-prising delivering and whirling a stream of heated air to. establish a vortex movement, feeding the particles to be dried into the stream of heated air for entrainment into the vortex to dry the particles, separating from the vortex movement by action of the vortex the slower drying particles from the air, removing with air from the vortex movement the substantially dried particles, introducing additional drying air to the vortex flow to intercept, further dry and reentrain the separated particles in the vortex movement, and recovering the substantially dried particles from the air removed from said vortex.

3. A method of rapidly drying particles of moist solid substances comprising delivering and whirling a stream of heated airinto a chamber to whirl the air downwardly therein in the form of a spiral and then upwardly centrally of the spiral to an exhaust outlet, whereby the slower drying particles are separated out by centrifugal force at the periphery of the whirling air and the more easily dried particles are carried by the air through the exhaust outlet, and introducing and whirling additional drying air into the lower portion'of the chamber in the form of an upward spiral to intercept, further dry and reentrain in the spiraling flow of the said first mentioned air the separated particles.

4. A method of rapidly drying moist solid'particles of casein curd and like substances in a confined s-pace comprising feeding the particles for suspension ina stream of heated air, introducing the air and entrained particles downwardly into said space in the form of a spiral and then upwardly centrally of the spiral, and introducing additional heated air at the bottom of the space to intercept particles to facilitate the drying thereof and their entrainment into the spiraling chamber to dry and entrain the separated parform of a spiral and then upwardly centrally of the spiral, and introducing additional air tangentially into the lower space to form an upward flow of air into the upper space to intercept particles gravitating toward the lower space and thereby further dry the particles'and re-entrain them into the spiraling movement.

6. A method of rapidly drying particles of moist solid substances in a plurality of concentrically arranged confined spaces; comprising feeding the particles for suspension in a stream of heated air, introducing the airiand entrained particles for movement upwardly into the outer space in the form of a spiral to the upper portion of the outer space, passing the air and particles entrained therein from the upper portion of the outer space tangentially into the inner space for movement downwardly in the form of a vortex, removing the air and'the particles entrained therein from the axial portion of the inner space, and introducing additional heated air adjacent the bottom of the inner'space to intercept particles released from the stream of air to facilitate the drying of the particles and the reentrainment thereof in said stream.

7. Apparatus for quickly drying particles of moist solid substances comprising means providing a chamber conically shaped at least in part,

means for feeding the particles for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangentially and adjacent the upper portion of said chamber to form a vortex movement in the chamber, an exhaust duct located centrally of the upper portion of said chamber for exhausting the air and substantially dried particles from the axial portion of said chamber, and means for .dntroducing additional air adjacent the bottom of said chamber to intercept particles which gravitate toward the bottom of said chamber to reentrain. them in the vortex movement.

8. Apparatus for quickly drying particles of moist solid substances comprising means providing a chamber conically shaped at least in part, means for feeding the particles for suspension in streams of hot air, means for introducing the air and the particles entrained there- 'in tangentially and adjacent the upper portion of said chamber to form a vortex movement in the chamber, an exhaust duct centrally of the upper portion of said chamber for exhausting the air and the particles maintained in suspension from the axial portion of saidchamber, means for introducing additional air adjacent the bottom of said chamber to intercept moisture re- .taining particles gravitating toward the bottom of said chamber to reentrain them in the vortex movement, and means for removing the particles from the air exhausted from said chamber.

9. Apparatus for quickly drying particles of moist solid substances comprising. means forming a chamber conically shaped at least in part, means for feeding the particles for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangen .,tially and adjacent the upper portion of said chamber to form a whirling movement therein,

means providing an exhaust duct centrally of the upper portion of said chamber for exhausting the air and particles maintained in suspension therein from said chamber, the coarser moisture retaining-particles being separated from the air and gravitating toward the bottom of the chamber, and means for introducing additional 'hot air tangentially and adjacent the bottom of said,

sage upwardly into the ticles for reentrainment in said whirling move ment for removal through said exhaust duct.

ing a chamber conically shaped at least in part, means for feeding the particles of substance for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangentially and adjacent the upper portion of said chamber to form a vortex movement in the chamber, the coarser moisture retaining particles of substance and any relatively heavy particles of foreign material present being separated from the air by centrifugal force and gravitating toward the bottom of said chamber, means for introducing adjacent the bottom of said chamber an upward flow of additional air to further dry and entrain the separated particles of substance for reentrainment in the vortex movement, an exhaust duct for the air and entrained particles located substantially coaxially of said chamber, and means at the bottom of said chamber for removing the particles graviticles from said chamber, a second chamber communicating with the bottom. of the first mentioned chamber, and ,means for introducing air tangentially into said second chamber for pasflrst mentioned chamber to intercept and thereby facilitate the drying of particles gravitating to the bottom of said first mentioned chamber.

l2.Apparatus for quickly drying particles of moist solid substances comprising means providing a chamber conically shaped at least in part, means for feeding the particles for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangentially and adjacent the upper portion of said chamber to form a vortex movement in the cham- V ber, an exhaust duct located centrally of the upper portion of said chamber so that the vortex movement is reversed and the air and entrained particles move in the form of a smaller vortex centrallyof the first mentioned vortex movement,

means to establish a suction through said exhaust duct,-and means to permit the entrance of additional air adjacent the bottom of said chamber to. intercept particles gravitating towards the bottom of the chamber and to reentain them into the aforementioned vortex r'novements. 7

13. Apparatus for quickly drying particles of moist solid substances comprising means providing a pair of similarly shaped chambers at least in part of coaxial form, one of the chambers being disposed in spaced relation to and within the upper portion of the other, means providing an opening arranged tangentially to said inner chamber and adjacent the upper portion thereof for communication with the outer chamber, means for feeding particles of the substance to be dried for suspension in a stream of hot air,

means for introducing the air and the particles of substance entrai ed therein tangentially adjacent the bottom portion of the outer chamber for upward whirling movement to and through the tangential opening into the inner chamber,

means providing an exhaust duct centrally of the upper portion of said inner chamber, and means communicating adjacent the bottom of the inner chamber for introducing additional airinto said inner chamber to facilitate the drying operation.

14. Apparatus for quickly drying particles of moist solid substances comprising means providing a chamber conically shaped at least in part, means for feeding the particles for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangentially and adjacent the upper portion of said chamber to form a vortex movement in the chamber, an exhaust duct located centrally of the upper portion of said chamber so that the vortex flow is reversed to exhaust the air and substantially dried particles from said chamber, a cone disposed in said chamber with the apex extending upwardly therein, means to support said cone in spaced relation to the sides of said chamber, and means for introducing additional air into said chamber for fiow upwardly between said cone and the sides of said chamber to intercept particles released from the vortex movement to further dry and reentrain them in the vortex.

15. Apparatus for quickly drying particles of moist solid substances comprising means providing a chamber conically shaped at leastin part, means for feeding the particles for suspension in a stream of hot air, means for introducing the air and the particles entrained therein tangentially and adjacent the upper portion of said chamber, an exhaust duct located centrally of the upper'portion of said chamber for exhausting the air and substantially dried particles from said chamber, a second chamber having a port communicating upwardly into the bottom of the first mentioned chamber, means for introducing an additional stream of air tangentially into said second chamber for passage through said port into said first mentioned chamber to facilitate the drying of particles gravitating to the bottom of said first mentioned chamber, and means associated with said port to direct the additional air upwardly axially of said first mentioned chamber.

WILLIAM B. WINTER. 

